Broken shadow render blender
This is a common problem with smooth-shaded, low-polygon-count models. It is caused by mismatching of the true shape of the polygonal model and the smoothed normals.
Here are three solutions:
1. Soften the lighting.
Increasing the size of the light will:
✔ Preserve the polygon count.
✔ Preserve the shader realism.
✖ Alter the look of the render.
2. Adjust the shadow termination.*
Adjusting the shadow termination offset will:
✔ Preserve the polygon count.
✖ Alter the shader realism.
✔ Preserve the look of the render.
3. Subdivide the geometry.
Subdividing the geometry will:
✖ Alter the polygon count.
✔ Preserve the shader realism.
✔ Preserve the look of the render.
* Blender 2.9+ Cycles only